...is that entire metal box dedicated only to bluetooth??? Or is it just the black box affixed on the outside?

If it's the entire box, that seems....kind of excessive

The massive steel box (not just the black bit) seems to be housing only Bluetooth, and yeah. It seems pretty silly. The BCU has been sitting on a shelf in my garage since the stereo swap and nothing else seems to have changed. I'll post if I notice something else... but yeah.

Maybe it had something to do with the XM? I don't know, we don't have a satellite subscription so I couldn't say - but we still get the test station with the updated radio so unless that maybe housed an XM antenna also, I got nothing.

Looks like the bulk of the folks posting in that thread are looking to replace the stereo with a non-OEM device, which is cool - I'd strongly recommend that anyone doing that sort of thing who doesn't want to cut/splice any of the harness cables for a '15 or earlier car use the BCU bypass and harness adapter I have listed in the third post of this thread - doing this will give you a harness for a '15 Sentra which opens up your aftermarket options a bit. Again, please do any of this at your own risk, and at all times refer to the service manuals if in doubt.

I'll go out to the Leaf this afternoon when the Mrs gets home and I'll yank out the harness adapter I made to get some pics, and will detail what's connected and where for that particular piece of the puzzle.

e: gonna have to wait for the weekend. Will get a pinout together of this harness adapter.

Here's the modified harness as described in my third post - it's based on an AX-NIS-ADDCAM1 harness adapter - but slightly modified.The Black and Yellow wires wrapped around the harness are a part of the harness adapter and are not used at all - I could have cut them off but I'm planning on using those for another Leaf modification later

Let's get a closer look at the connections:

In this angle, I have the female end (the end that the male connection from the car plugs in to) at the bottom, and the male end (which plugs into the stereo) at the top.Let's start with the top row of pins from the male connector (to radio) in the top half of this picture. There are six wires which are connected 1:1 - that is - they go from the same place on the car's harness to the same place on the new radio. Other than the 6 pins connected at the leftmost connection on the top row, the entire top row is empty as it connects to the new radio - but not so on the female end which connects to the car (bottom half of this picture). Although the 6 pins are present - there are another two pins (green/white and blue/black) occupying that row as connected from the car. These are carrying the MIC+/MIC- and need to be moved to their new location - this happens to be on the second row.

Here's the second row:Now, this is a little confusing to look at, because these connectors aren't really "side-by-side" like this in real life - so the connections are flipped. The left plug is the female (to car) and the right is the male (to radio). You can see where the green/white and blue/black connections are coming from the car (left half of image, top row, left) - and now where they're going to (right half of image, bottom row, right). In between those pins there is a red wire - this is the +5v output from the radio which is providing the mic power through a long wire down to the BCU harness.

If you refer to the images in my first post, you'll see that only 4 of the top row pins are probably needed (as the old radio had 6 pins and the new one only 4). This would mean you could possibly use the existing wiring from either of those two pins (the old radio used them for COMM high/low to the BCU, now removed from the car) as your method of delivering +5v Mic Power to the trunk - saving you from doing what I did and running a new wire to the trunk. I don't know if you might damage anything running current through those wires - obviously only try this (or anything I posted) if you are willing to take the risk of damaging stuff - but hypothetically, what you'd do is move one of those two spare pins from the top row between the green/white and blue/black in place of my red wire, which runs to the trunk to the BCU harness, and then patch that to the Mic Power input.

Here's a decent shot of the connection which is going into the radio, with the red +5v doorbell wire I ran down to the trunk. That red pin at the bottom right of the radio end is (as far as I know) the easiest +5v output to get at from the radio itself.There are 4 other pins on the bottom row which will be a 1:1 connection.

Someone asked about the Bluetooth Control Unit, and was asking if that's all it does. Let's find out:

The unit pulled from the car

Connections on the device

Black box pulled off the top; looks like this particular component is for comms between the device itself and passenger's phones

Hell of a lot of silicon for a basic bluetooth module..

I see a Texas Instruments OMAP processor, some memory of some description just underneath and to the left of the OMAP chip, beneath all of this is the Bluetooth radio ("csr" labelled chip, upside-down). The square chip on the right is another TI processor (TMS 470).

What the hell is this thing for?!? That is a hell of a lot of power for just handling phone calls!I did bench test the old radio - it still does "radio" stuff (obviously though it never streamed Bluetooth) but since just about everything else seems to work, I'm perplexed.

That....is really weird. I don't understand what all of that hardware is for; also, that TI chip has really bizarre stuff like a DSP core that includes video stuff (???). I'm also baffled why this thing has to live in the trunk???

I don't understand that either; plenty of companies fit full-featured bluetooth capabilities in a form factor dramatically smaller than that. Or, translation: if nissan made a blue-tooth enabled cell phone, it'd be twice the size of a VHS tape???